The invention regards a process and a device for the manufacture of connecting seams between overlapping material segments made of elastomers or thermoplastic materials, especially roofing and sealing strips.
In the case of, for example, flat roofs with so called roofing or sealing strips, the creation of joints, especially flat ones, between the individual sealing strips or sheets creates enormous difficulties.
As a rule, sheets composed of individual strips are installed. The prefabrication of sheets with a stationary device permits the easy creation of a permament watertight union by vulcanizing the individual overlapping segments of the connecting seam. The connecting seams between the individual strips manufactured on site are made by, for example, gluing. The glued seam is generally covered by an adhesive strip.
In the case of a frontal union of sheets made up of individual strips, so called T-joints are created. When the seams of both sheets converge, cross-joints are formed. These areas, due to the stepwise configuration of the connecting seam, create excessively weak spots and have to be additionally reinforced by applying sealing paste or a similar material.
These glued joints have considerable disadvantages compared to those made by vulcanization. The sheets can virtually not be installed without stress. However, since glue requires a certain amount of time for curing, the stress generated by the glue hardening process in the seam area has a negative effect on the quality of the glued joint. Even after the glue has hardened, the resistance of the bonded area remains temperature dependent. In the event of high temperatures (roofs can reach temperatures above 80.degree. C.) the glued joint softens. In time, the effects of fluctuating temperatures can damage the glued joint to such an extent that it starts leaking. In this case extensive and costly repair work is necessary.
So far, the creation of flat vulcanized connecting seams made on site failed due to the fact that it was not possible to securely hold the strips or sheets during vulcanization since the vulcanization device was unable to hold the flat sheets, and consequently, the seam. Due to this, the pressure on the seam necessary for vulcanization can only be applied by the weight of the vulcanization device itself. Consequently, correspondingly heavy devices would be necessary, but these would be extremely difficult to handle on construction sites, especially on roofs.
In order to avoid glued unions it has already been suggested to join the sheets with upright vulcanized seams. The edges of the installed sheets are bent at a right angle, are pressed against one another in the seam area, and are subsequently vulcanized. In this case, the vulcanization device can hold the seam and the necessary pressure can be applied by mechanical or hydraulic displacement of both pressure bearing surfaces against one another.